An Active Atlantic Hurricane Season Still Predicted by NOAA, CSU, and TSR

As we stand on the cusp of the peak part of hurricane season, all of the major groups that perform long-range seasonal hurricane forecasts are still calling for an active 2013 Atlantic hurricane season. NOAA forecasts an above-normal and possibly very active Atlantic hurricane season in 2013, in their August 8 outlook. They give a 70% chance of an above-normal season, a 25% chance of an near-normal season, and 5% chance of a below-normal season. They predict a 70% chance that there will be 13 - 19 named storms, 6 - 9 hurricanes, and 3 - 5 major hurricanes, with an Accumulated Cyclone Energy (ACE) 120% - 190% of the median. If we take the midpoint of these numbers, NOAA is calling for 16 named storms, 7.5 hurricanes, 4 major hurricanes, and an ACE index 155% of normal. This is well above the 1981 - 2010 average of 12 named storms, 6 hurricanes, and 3 major hurricanes. Hurricane seasons during the active hurricane period 1995 - 2012 have averaged 15 named storms, 8 hurricanes, and 4 major hurricanes, with an ACE index 151% of the median.

Figure 1. Tropical Storm Dorian on July 25, 2013, when the storm reached peak intensity--sustained winds of 60 mph. Formation of early-season tropical storms like Chantal and Dorian in June and July in the deep tropics is usually a harbinger of an active Atlantic hurricane season. Image credit: NASA.

NOAA cites five main reasons to expect an active remainder of hurricane season:

1) Sea Surface Temperatures (SSTs) are above average in the Main Development Region (MDR) for hurricanes, from the coast of Africa to the Caribbean. As of August 9, SST were 0.4°C (0.8°F) above average.2) Trade winds are weaker than average across the MDR, which has caused the African Monsoon to grow wetter and stronger, the amount of spin over the MDR to increase, and the amount of vertical wind shear to decrease. 3) No El Niño event is present or expected this fall.4) There have been two early-season tropical storms in the deep tropics (Tropical Storms Chantal and Dorian), which is generally a harbinger of an above-normal season.5) We are in an active hurricane period that began in 1995.

Colorado State predicts a much above-average hurricane seasonA much above-average Atlantic hurricane season is on tap for 2013, according to the seasonal hurricane forecast issued August 2 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 18 named storms, 8 hurricanes, and 3 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 142. The forecast calls for an above-average chance of a major hurricane hitting the U.S., both along the East Coast (40% chance, 31% chance is average) and the Gulf Coast (40% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also above average, at 53% (42% is average.)

Analogue yearsThe CSU team picked five previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: cool neutral ENSO conditions and slightly above-average tropical Atlantic sea surface temperatures. Those five years were 2008, a very active year with 16 named storms and 4 major hurricanes--Gustav, Ike, Paloma, and Omar; 2007, an active year with 15 named storms and two Category 5 storms--Dean and Felix; 1996, an above average year with 13 named storms and 6 major hurricanes--Edouard, Hortense, Fran, Bertha, Isidore, and Lili; 1966, an average year with 11 named storms and 3 major hurricanes--Inez, Alma, and Faith; and 1952, a below average year with 7 named storms and 3 major hurricanes. The average activity during these five analogue years was 12.4 named storms, 7.2 hurricanes, and 3.8 major hurricanes.

TSR predicts an above-average hurricane season: 14.8 named stormsThe August 6 forecast for the 2013 Atlantic hurricane season made by British private forecasting firm Tropical Storm Risk, Inc. (TSR) calls for an active season with 14.8 named storms, 6.9 hurricanes, 3 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 121. The long-term averages for the past 63 years are 11 named storms, 6 hurricanes, 3 intense hurricanes, and an ACE of 103. TSR rates their skill level as good for these August forecasts--47% - 59% higher than a "no-skill" forecast made using climatology. TSR predicts a 58% chance that U.S. land falling activity will be above average, a 26% chance it will be near average, and a 16% chance it will be below average. They project that 4 named storms will hit the U.S., with 1.8 of these being hurricanes. The averages from the 1950-2012 climatology are 3.1 named storms and 1.4 hurricanes. They rate their skill at making these August forecasts for U.S. landfalls just 9% - 18% higher than a "no-skill" forecast made using climatology. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.4 named storms, 0.6 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR's two predictors for their statistical model are the forecast July - September trade wind speed over the Caribbean and tropical North Atlantic, and the forecast August - September 2013 sea surface temperatures in the tropical North Atlantic. Their model is calling for warmer than average SSTs and near average trade winds during these periods, and both of these factors should act to increase hurricane and tropical storm activity.

Figure 2. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August), using the Mean Squared Error. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.

Figure 3. Comparison of the percent improvement in mean square error over climatology for seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 2003-2012, using the Mean Square Skill Score (MSSS). The figure shows the results using two different climatologies: a fixed 50-year (1950 - 1999) climatology, and a 2003 - 2012 climatology. Skill is poor for forecasts issued in December and April, moderate for June forecasts, and good for August forecasts. Image credit: Tropical Storm Risk, Inc.

FSU predicts an above-average hurricane season: 15 named stormsThe Florida State University (FSU) Center for Ocean-Atmospheric Prediction Studies (COAPS) issued their fifth annual Atlantic hurricane season forecast on May 30, calling for a 70% probability of 12 - 17 named storms and 5 - 10 hurricanes. The mid-point forecast is for 15 named storms, 8 hurricanes, and an accumulated cyclone energy (ACE) of 135. The scientists use a numerical atmospheric model developed at COAPS to understand seasonal predictability of hurricane activity. The model is one of only a handful of numerical models in the world being used to study seasonal hurricane activity and is different from the statistical methods used by other seasonal hurricane forecasters such as Colorado State, TSR, and PSU (NOAA uses a hybrid statistical-dynamical model technique.) The FSU forecast has been one of the best ones over the past four years:

Penn State predicts an above-average hurricane season: 16 named stormsA statistical model by Penn State's Michael Mann and alumnus Michael Kozar is calling for an active Atlantic hurricane season with 16 named storms, plus or minus 4 storms. Their prediction was made using statistics of how past hurricane seasons have behaved in response to sea surface temperatures (SSTs), the El Niño/La Niña oscillation, the North Atlantic Oscillation (NAO), and other factors. The statistic model assumes that in 2013 the May 0.87°C above average temperatures in the MDR will persist throughout hurricane season, the El Niño phase will be neutral to slightly warm, and the North Atlantic Oscillation (NAO) will be near average.

The PSU team has been making Atlantic hurricane season forecasts since 2007, and these predictions have done pretty well, except for in 2012, when an expected El Niño did not materialize:

UK Met Office predicts a slightly above-average hurricane season: 14 named stormsThe UKMET office forecast for the 2013 Atlantic hurricane season, issued May 13, calls for slightly above normal activity, with 14 named storms, 9 hurricanes, and an ACE index of 130. In contrast to the statistical models relied upon by CSU, TSR, and NOAA, the UKMET model is done strictly using two dynamical global seasonal prediction systems: the Met Office GloSea5 system and ECMWF system 4. In 2012, the Met Office forecast was for 10 tropical storms and an ACE index of 90. The actual numbers were 19 named storms and an ACE index of 123.

Figure 4. Total 2013 Atlantic hurricane season activity as predicted by twelve different groups.

NOAA predicts a below-average Eastern Pacific hurricane seasonNOAA's pre-season prediction for the Eastern Pacific hurricane season, issued on May 23, calls for a below-average season, with 11 - 16 named storms, 5 - 8 hurricanes, 1 - 4 major hurricanes, and an ACE index 60% - 105% of the median. The mid-point of these ranges gives us a forecast for 13.5 named storms, 6.5 hurricanes, and 2.5 major hurricanes, with an ACE index 82% of average. The 1981 - 2010 averages for the Eastern Pacific hurricane season are 15 named storms, 8 hurricanes, and 4 major hurricanes.

NOAA predicts a below-average Central Pacific hurricane seasonNOAA's pre-season prediction for the Central Pacific hurricane season, issued on May 22, calls for a below-average season, with 1 - 3 tropical cyclones. An average season has 4 - 5 tropical cyclones, which include tropical depressions, tropical storms, and hurricanes. Hawaii is the primary land area affected by Central Pacific tropical cyclones.

West Pacific typhoon season forecast not available this yearDr. Johnny Chan of the City University of Hong Kong usually issues a seasonal forecast of typhoon season in the Western Pacific, but did not do so in 2012 or 2013. An average typhoon season has 27 named storms and 17 typhoons. Typhoon seasons immediately following a La Niña year typically see higher levels of activity in the South China Sea, especially between months of May and July. Also, the jet stream tends to dip farther south than usual to the south of Japan, helping steer more tropical cyclones towards Japan and Korea.

Quiet in the Atlantic this weekendThere are no Atlantic threat areas to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming seven days. However, there are some indications that the atmosphere over the tropical Atlantic will become more conducive for tropical storm formation beginning around August 15. The Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days, may move into the Atlantic then, increasing tropical storm formation odds. At the same time, the computer models are indicating an increase in moisture over the tropical Atlantic, due to a series of tropical waves expected to push off of the coast of Africa. There will also be several eastward-moving Convectively-Coupled Kelvin Waves (CCKWs) traversing the Atlantic during that period. These atmospheric disturbances have a great deal of upward-moving air, which helps strengthen the updrafts of tropical disturbances. Formation of the Eastern Pacific's Hurricane Gil and Henriette were aided by CCKWs. These same CCKWs will cross into the Atlantic and increase the odds of tropical storm formation during the period August 15 - 20.

Quoting 2383. Tribucanes:Utor is beautiful. I get why Sar is so sensitive though, there are probably dozens at the minimum in the Philippines who have absolutely no idea, this time tomorrow they will no longer be here. They know Utor is bearing down on them, but they don't know that He will bring death to their door. Over 150,000 people die each day in the world, it's just the nature of our fragile existence. It's sad though, praying for the Philippines tonight. What a beast of a storm.

One critical part of possessing a desire for hurricane landfalls is humility and compassion. I want another hurricane strike so much I can hardly stand it. However, if by some chance we DID get a repeat of Gustav, Katrina, Rita, whatever... I would seal my tongue and keep thoughts of "excitement" to myself. It's one thing to mouth off those words during quiet periods, when no one's actually in any tangible danger or ostensible threat of dying. It's quite another to openly espouse such passions when people actually ARE going to die.

I think that's why JFV became so infamous; it wasn't his desire for hurricanes that people thought was immoral. It was his lack of tact.

Quoting 2377. KoritheMan:Anyone know where I can find a western Pacific tracking map to create forecast tracks for storms in that basin? I've scoured the net tirelessly for them, but I'm not having any luck.

This is the best I can find and hopefully it is what you're looking for. WPac tracking map

Utor is beautiful. I get why Sar is so sensitive though, there are probably dozens at the minimum in the Philippines who have absolutely no idea, this time tomorrow they will no longer be here. They know Utor is bearing down on them, but they don't know that He will bring death to their door. Over 150,000 people die each day in the world, it's just the nature of our fragile existence. It's sad though, praying for the Philippines tonight. What a beast of a storm.

Quoting Tribucanes:Pensacola Doug at least tries to make a counter argument, basing that urban heating in large cities have unfairly been used to measure the rise in global temps. Stating large cities have been warming at faster rates than rural areas with small populations. That's true. Atlanta has been warming very quickly over the last thirty years for the very obvious reasons Doug stated, while more rural towns haven't warmed as quickly. The warming climate numbers scientists use to measure global temps though is global means, encompassing all towns/cities and every other area on the planet for all seasons. The conclusion is concise, the planet is warming at rates not seen in human times because of CO2 output. The North Pole is a perfect example of this, it's warming much faster than other areas, seas are rising, and the Northern Hemisphere's warming has caused the jet stream to change, and it has nothing to do with the number of large heavily populated cities at the North Pole. More moisture/heat equals more extreme floods and more extreme droughts. It's a pretty simple equation: as more CO2 is released temperatures can but rise. Doug stated CO2 levels are at the low range of where plants can survive. That's true. For many animals, insects, fish, that's not the same story.

Without getting into the whole Co2 issue, the heat island thing is really more pervasive than one might think. I live in a town of only 13,000, and the population has actually fallen about 5% since 2000, mainly because we've had so many textile mills close down. During that same period. "out of town" has been more or less paved over, as a SuperWalmart and several shopping centers have been built. We are the only city of any size within about 40 miles, so we are still a shopping destination. The average high has crept up about one degree in the last 10 years, and the average low,even in winter, has risen by the same amount. We are surrounded by a huge lake, so it's very easy to experience temperature changes driving from my home to these shopping areas. On a summer night, you can feel the obvious increase in temperature with all this blacktop compared to driving across the lake. In the winter, there will be puddles in the woods with ice on them while the puddles in the Walmart parking lot remain ice-free. If this heat island effect is so obvious and pronounced in a small town like mine, imagine New York, Los Angeles, Beijing, or New Delhi. I don't know if we really have a handle on this, but I think the cumulative effect must be huge.

Quoting 2376. Ameister12:As I see it right now, Utor is pretty much an unavoidable disaster for the Philippines. It really doesn't matter if it ends up remaining (for some reason) a category 3, or gets upgraded to a category 4/5, it's gonna cause a lot of destruction. It's rating means nothing.

Agreed. Regardless of its strength, high winds, heavy rain, and storm surge will still result in catastrophic damage.

As I see it right now, Utor is pretty much an unavoidable disaster for the Philippines. It really doesn't matter if it ends up remaining a category 3, or gets upgraded to a category 4/5, it's gonna cause a lot of destruction. Its rating means nothing.

Quoting 2359. sar2401:I realize it's just enthusiasm, but Aussie posted just a few hours ago that his wife is from the part of the Philippines that's about to get hit and has family there. Just as a courtesy to fellow bloggers, we need to remember this is a worldwide blog, and EPAC storms are not just there to amuse us.

Quoting 2359. sar2401:I realize it's just enthusiasm, but Aussie posted just a few hours ago that his wife is from the part of the Philippines that's about to get hit and has family there. Just as a courtesy to fellow bloggers, we need to remember this is a worldwide blog, and EPAC storms are not just there to amuse us.

Oh, I agree. I don't really hide that I want hurricane landfalls, and that I like to forecast and experience them, but if you notice, I really only say that during quiet periods. I wouldn't, in a million years, consider saying something like that during an active storm, for what should be obvious reasons to anyone. In those particular cases, I would keep those thoughts entirely to myself.

As someone who wants to experience major hurricane landfalls, I agree that comments like this should be kept to oneself.

However, I've known Isaac for awhile now, and I don't think he meant anything by it.

Let it go.

I realize it's just enthusiasm, but Aussie posted just a few hours ago that his wife is from the part of the Philippines that's about to get hit and has family there. Just as a courtesy to fellow bloggers, we need to remember this is a worldwide blog, and EPAC storms are not just there to amuse us.

They just erased a circle that never had a chance anyway. I'm not sure why the NHC even bothers with a disorganized system that is for sure making landfall in 24 hours. I guess they just want to show they're paying attention.

The population of the Philippines is estimated to reach 100 million this year up from 27 million in 1960. A lot of land on hills has been cleared for agriculture, forestry and dwellings. It's a crowded country.

Quoting KoritheMan:I have a friend at work that's from the Philippines. I'm not sure which part, but perhaps he could educate me on the building codes in the area, and the structural vulnerability to major typhoons.

Parts of Metro Manila are pretty good. The huge slum areas are always a disaster. Most other parts of the Philippines, the building code doesn't matter much, it's flooding and landslides that are the killers.

Quoting 2340. KoritheMan:I have a friend at work that's from the Philippines. I'm not sure which part, but perhaps he could educate me on the building codes in the area, and the structural vulnerability to major typhoons.

Building codes? Third world shacks on deforested mountains and hills is the story Kori.

I asked the question about FIM yesterday. FIM7 & 8 are lower resolution, so less accurate than FIM9. FIM9 goes out 7 days, whereas 7 and 8 go out 14. Any more info than that and an expert will have to answer.

Actually both FIM 8 and FIM 9 are pretty good track models with FIM 9 having a reslotion of 15km (same or about the same as the Euro) and FIM 8 a resolution of 30KM which is comparable to GFS resolution of around 28KM.

As for storm track accuracy between FIM 9, FIM 8, GFS, and Euro this is the best info I have seen in my brief research...it is a large online noaa/hfip pdf file so may take a minute to load but definitely recommend a look at if interested:Link